Volume control and switch for radiocircuits



Oct. 9, 1928.

D. R. LOVEJOY VOLUME CONTROL AND SWITCH FOR RADIOCIRCUITS Filed July 15, 1926 I I ENT fl/m/n/ff x? Lorgo ATTORNEY Patented @cta il, 19%,

IDIEMIVII'ET RQS$ LOVEJ U31, OPE NEW YORK, N. 511, Ae'iSIGNQR, BY ASSIGNMENTS, 120 AMERICAN BOSCH MAGNETU CORPORATION, @113 SPRINGFIELD, MASSACHUSETTS, A

, CQRZPQRATION 015 NEW "SE13.

VQ LUME CONTROL AND S'WITCll-ll ZEGR- RAD'EUCIRCUZTS.

application filed; July 15,

The present invention relates to a volume control and switch of unitary construction for radio circuits having a plurality of thermionic tubes with heater elements as audions with filaments.

111 such circuits, a rheostat or rheostats have been used with the heater elements of one or more tubes, sometimes the radio frequency tubes and sometimes the audio frequency tubes and sometimes both, to control the volume or strength of the broadcasted or received waves, but so far as 1 am aware the switch was always a separate device or controlled in an independent operation so as to interrupt all the filament current irrespective of the position of the rheostat or rheostats. Not only did this require separate devices or operations and extra connecting wires for the purpose, but usually the switch had to interrupt a larger current and sometimes produced an excessive volume upon starting.

lln accordance with my invention, the volume control and switch are combined into a unitary structure operated by a single control knob or handle in a continuous movement. This is accomplished by comb'ning a switch with a rheostat and so constructing and arranging the parts of the unitary structure that the switch is'electrically connected to the rheostat either in series or in parallel. in the preferred embodiment of the device, to a conventional rheostat having a resfstor contact arm conductively fastened to a shaft for rotation therewith, there is added a notched conducting member also conductively fastened to the shaft and a switch contact arm. or fingers fastened to the stationary insulating body in such position as to lie inefi'ectively in the notch when the con-. tact arm is at the off position. disengaged from its resistor. or at the point of maximum resistance thereof. in the preferred form of circuit embodying this device, the filament or filaments undcr control are connected to the end of the resistor away from the oil position of the switch so as to reduce the current to the minimum before interruption and to prevent-excessive volume upon start ing, and the. remaining filaments are connected in any suitable grouping to the switch, an adjustably-fixed resistance being in series with the source of current and all the filaments'to predetcrmine the maximum 1926. Serial No. 122,560.

current thereto, and a second resistance being in series with those filaments not under control. in this circuit all filaments are grounded and the ungrounded termlnal of the source of current is connected to the switch.

in the accompanying drawings illustrating the preferred form of my invention as applied, as an example, to the control of the filament of the first radio frequency stage of a radio receiving circuit and with the remaining filaments grouped in parallel.

hi 1 is an elevation of the rear of the unitary volume control and switch mounted on a panel broken away; Fig. 2 is a side elevation thereof; Fig. 3 is a central section of the device, partly in ele ation; Fig. i is a section on line 4% of Fig. 3; and Fig. 5 is a d agram of the radio circuit embodying the device. 'i g The rheostat, of conventional form, has an insulating block 1, and a resistor 2 of circular form comprising an insulating support 3 with a resistor composed of suitable resistance wire 4: wound thereon. One end of the wire is fastened to the binding post 5 and the other end is fastened to the support 3 short of the binding post 6. The shaft 7 has a knob 8 fastened to oneend and the expanding screw 9 threaded in the other end to secure the sleeve 10 to the shaft. rheostat contact arm 11 is conductively fas tened to the sleeve by the nut 12 so as to turn with the "shaft from one extreme position in engagement with the insulating tube 13 surrounding the terminal 5 to the other extreme position in engagement with the insulating tube 1 1 surrounding the terminal 6.

The conducting member 15 with rim 16 is conductively fastened to the sleeve 10'and has a notched or cut-away portion at 17. The spring fingers 18 are fastened to the insulating block 1 by the binding post 19. These fingers press against the outside surfaces of the rim 16 and are so located with respect to the cut-away portion at 17 that when the arm 11 movcs'out of engagement with the resistance wire l, the lingers 18 spring into the cut-away portion out of engagement with the rim 16. The conducting member 15 is connected to the binding post 6 through the conducting strip 20.

' lin Fig. 5 the binding post 5 of the unitary volume control and switch is con Mil the detector tube and both audio frequency tubes, are connected in a parallel group to the binding post 19 through the fixed resistance 23. The positive terminal of the battery 24 is connected to binding post 6 andthe negative terminal is connected to an adjustably-fixed resistance 25 which is grounded. In the position of the shaft shown in Fig. 5, the current flows from the battery 24 to the conducting member 15 where it divides, one part passing through the fingers 18 to the binding post 19 and thence to the filaments 22 in parallel, and the other part passing through the active portion of the resistance wire 4 to binding post 5 and thence to the filament 21. The current flowing to filament 21 can bevaried throughout a range determined by the resistance wire 4:.to vary the filament emission and therefore the amplification of the first radio frequency tube and thus the volume of sound from a loud speaker connected to the last audio frequency tube. Throughout all this-variation, the current to all the filaments 22 remains unaltered.

To start the set into operation, the shaft 7 is turned in the anticlockwise direction in- Fig. 5 from the off position at the extreme left to a position in which the desired volume from the loud speaker is attained, and to stop the operation, the shaft is turned in the opposite direction until the contact arm 11 abuts the insulating tube 14.

If desired the positive terminal of the battery 24.may be connected to the binding post 19, instead of 6 in Fig. 5, and the fixed resistance 23 then connected to binding post 6, instead of 26, in which case the switch comprising the fingers 18 and the conducting member 15, 16 would be in series, instead of parallel, with the rheostat comprising the contact arm 11 and resistor 4.

Having thus claimed my invention, what I claim is:

1'. A unitary volume control and switch for radio circuits, comprising a resistor, a rotatable shaft, a contact arm rotatable with the shaft into and out of engagement with the resistor, and two conducting members one of which is rotatable with the shaft into and out of engagement with the other and electrically connected to the contact arm, the parts being so constructed and arranged that there is one position of the shaft in Which the rotatable conducting member and the contact member are disengaged from the other conducting member and the resistor respectively.

2. A unitary volume control and switch for radio circuits, comprising a resistor of arcuate form, a rotatable shaft, a contact arm fastened to the shaft for rotation in engagement with the resistor, a stationary contact arm, a conducting member fastened to the shaft in electrical connection with the rotatable contact arm and having a notched member cooperative with the stationary contactarm, and an abutment cooperative with one of the rotatable parts to limit the rotation of the shaft at the position in which the stationary contact arm is within said notch.

In testimony whereof I atfix my signature.

DIMMITT 'R. LOVEJOY. 

